Relationships Between Behavioral Rhythms, Plasma Corticosterone and Hypothalamic Circadian Rhythms

Abstract

Circadian rhythms in physiological processes and behaviors were compared with hypothalamic circadian rhythms in norepinephrine (NE) metabolites, adrenergic transmitter receptors, cAMP, cGMP and suprachiasmatic nucleus (SCN) arginine vasopressin (AVP) in a single population of rats under D:D conditions. Eating, drinking and locomotor activity were high during the subjective night (the time when lights were out in L:D) and low during the subjective day (the time when lights were on in L:D). Plasma corticosterone concentration rose at subjective dusk and remained high until subjective dawn. Binding to hypothalamic alpha 1- and beta-adrenergic receptors also peaked during the subjective night. Cyclic cGMP concentration was elevated throughout the 24-hr period except for a trough at dusk, whereas DHPG concentration peaked at dawn. Arginine vasopressin levels in the suprachiasmatic nucleus peaked in the middle of the day. No rhythm was found either in binding to the alpha 2-adrenergic receptor, or in MHPG or cAMP concentration. Behavioral and corticosterone rhythms, therefore, are parallel to rhythms in hypothalamic alpha 1- and beta-receptor binding and NE-release. Cyclic GMP falls only at dusk, suggesting the possibility that cGMP inhibits activity much of the day and that at dusk the inhibition of nocturnal activity is removed. SCN AVP, on the other hand, peaking at 1400 hr, may play a role in the pacemaking function of the SCN that drives these other rhythms.

Prenatal Exposure to Interleukin-6 Results in Hypertension and Increased Hypothalamic-Pituitary-Adrenal Axis Activity in Adult Rats

“…Analysis of the circadian variation in CORT levels (0800 -1700 h) in control rats showed that the peak was reached just before the end of the light period, as in other studies (39,40). Prenatal IL-6 exposure therefore seems to modify the light period pattern, as reflected by largely constant and increased levels of CORT.…”

Prenatal stress alters circadian activity of hypothalamo–pituitary–adrenal axis and hippocampal corticosteroid receptors in adult rats of both gender

“…Prenatal stress does not influence ACTH release, which in our study did not show circadian rhythmicity. This absence of ACTH rhythmicity has already been reported: indeed, ACTH rhythm is known to be of low amplitude, and frequently not significant over a 24-h period (Wilkinson et al, 1979(Wilkinson et al, , 1981Kafka et al, 1986), which may largely be due to the high frequency of its pulsatility (Gudmundsson and Carnes, 1997). Such divergence in ACTH and corticosteroid levels observed is common.…”

Chronic hyperammonemia alters the circadian rhythms of corticosteroid hormone levels and of motor activity in rats

“…Steroidogenesis is modulated by nitric oxide (Del Punta et al,1996; Hanke et al,1998; Cymeryng et al,1999) and cGMP (Nambi et al,1982). The HPA axis is also modulated by nitric oxide and cGMP (Kafka et al,1986; Gadek‐Michalska and Bugajski,2008). This suggests the possibility that altered function of the nitric oxide‐cGMP pathway could contribute to altered rhythms of corticosterone release.…”